We propose to resurvey the 2,872 persons treated in infancy with x- rays for alleged thymic enlargement. As controls their untreated siblings will also be studied. Besides information about radiation- induced neoplasms, we also will make a determined effort to obtain information about auto-immune diseases in the irradiated and control population. Incidental information obtained in the last survey strongly suggested an increased incidence of auto-immune type illnesses in the irradiated population. Studies on B and T lymphocytes indicated a marked depression of T lymphocytes in the irradiated population. The survey of 606 women treated with x-rays for acute post-partum mastitis has been completed. As controls, we have surveyed 526 untreated sisters and 550 women patients at the New York Hospital not treated with x-rays. The treated women have an incidence of breast cancer that is 2 1/2 times expectation. The sisters may have a slight increase over expectation but the women with acute mastitis do not. Because of their high risk, irradiated women will be called to SMH for mammography and thermography. The 1,000 subjects given x-ray treatments to the head for lympoid hyperplasia of the nasopharynx will be surveyed. As controls, we will also survey 400 persons with the same diagnosis treated with intranasal radium capsules and the almost 3,000 untreated siblings.